/**
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0.
 */

#pragma once

#include <smithy/identity/signer/AwsSignerBase.h>
#include <smithy/identity/identity/AwsCredentialIdentityBase.h>
#include <aws/core/auth/AWSCredentials.h>
#include <aws/crt/auth/Credentials.h>

#include <aws/core/http/HttpRequest.h>
#include <aws/core/auth/signer/AWSAuthSignerHelper.h>
#include <aws/crt/http/HttpConnection.h>
#include <aws/crt/http/HttpRequestResponse.h>
#include <condition_variable>
#include <mutex>
#include <smithy/identity/signer/built-in/SignerProperties.h>
#include <smithy/identity/auth/AuthSchemeResolverBase.h>

namespace smithy {
    static const char* UNSIGNED_PAYLOAD = "UNSIGNED-PAYLOAD";
    static const char* EMPTY_STRING_SHA256 = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
    static const char v4AsymmetricLogTag[] = "AWSAuthSymmetricV4Signer";
    static const char* USER_AGENT = "user-agent";
    static const char* X_AMZN_TRACE_ID = "x-amzn-trace-id";

    /**
     * A smithy SigV4 signer wrapper on top of legacy SDK SigV4 signer
     * TODO: refactor into own signer using smithy design
     */
    class AwsSigV4aSigner : public AwsSignerBase<AwsCredentialIdentityBase> {

    public:
        using SigV4aAuthSchemeParameters = DefaultAuthSchemeResolverParameters;
        explicit AwsSigV4aSigner(const Aws::String& serviceName, const Aws::String& region)
            :  m_serviceName(serviceName), m_region(region)
        {
        }

        //for legacy constructors
        explicit AwsSigV4aSigner(const Aws::String& serviceName, const Aws::String& region, Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy policy)
            :  m_serviceName(serviceName), m_region(region), m_policy(Aws::MakeShared<Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy>("AwsSigV4aSigner", policy))
        {
        }

        explicit AwsSigV4aSigner(const Aws::String& serviceName, const Aws::String& region, Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy policy, bool urlEscape)
            :  m_serviceName(serviceName), m_region(region), m_policy(Aws::MakeShared<Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy>("AwsSigV4aSigner", policy)), m_urlEscape{urlEscape}
        {
        }

        SigningFutureOutcome sign(std::shared_ptr<HttpRequest> httpRequest, const AwsCredentialIdentityBase& identity, SigningProperties properties) override
        {
            return sign(httpRequest, identity, properties, m_region, m_serviceName, m_expirationTimeInSeconds, Aws::Crt::Auth::SignatureType::HttpRequestViaHeaders);
        }

        SigningFutureOutcome presign(std::shared_ptr<HttpRequest> httpRequest, const AwsCredentialIdentityBase& identity, SigningProperties properties, const Aws::String& region, const Aws::String& serviceName, long long expirationTimeInSeconds) override
        {
            Aws::String signingRegion = !region.empty() ? region : m_region;
            Aws::String signingServiceName = !serviceName.empty() ? serviceName : m_serviceName;
            Aws::Crt::Auth::SignatureType signatureType = Aws::Crt::Auth::SignatureType::HttpRequestViaQueryParams;

            const auto credentials = [&identity]() -> Aws::Auth::AWSCredentials {
                if(identity.sessionToken().has_value() && identity.expiration().has_value())
                {
                    return {identity.accessKeyId(), identity.secretAccessKey(), *identity.sessionToken(), *identity.expiration()};
                }
                if(identity.sessionToken().has_value())
                {
                    return {identity.accessKeyId(), identity.secretAccessKey(), *identity.sessionToken()};
                }
                return {identity.accessKeyId(), identity.secretAccessKey()};
            }();

            //don't sign anonymous requests
            if (credentials.GetAWSAccessKeyId().empty() || credentials.GetAWSSecretKey().empty())
            {
                return  SigningFutureOutcome(std::move(httpRequest)) ;
            }
            return sign(httpRequest, identity, properties, signingRegion, signingServiceName, expirationTimeInSeconds, signatureType);
        }

        virtual ~AwsSigV4aSigner() {};
    protected:

        bool createAwsSigningConfig(
            std::shared_ptr<Aws::Crt::Auth::Credentials>& crtCredentials,
            const Aws::Http::HttpRequest& request,
            const Aws::String& serviceName,
            const Aws::String& region,
            Aws::Crt::Auth::AwsSigningConfig& awsSigningConfig,
            bool signBody,
            Aws::Crt::Auth::SignatureType signatureType) const
        {
            awsSigningConfig.SetSigningAlgorithm(static_cast<Aws::Crt::Auth::SigningAlgorithm>(Aws::Auth::AWSSigningAlgorithm::ASYMMETRIC_SIGV4));
            awsSigningConfig.SetSignatureType(signatureType);
            awsSigningConfig.SetRegion(serviceName.c_str());
            awsSigningConfig.SetService(region.c_str());
            awsSigningConfig.SetSigningTimepoint(GetSigningTimestamp().UnderlyingTimestamp());
            awsSigningConfig.SetUseDoubleUriEncode(m_urlEscape);
            awsSigningConfig.SetShouldNormalizeUriPath(true);
            awsSigningConfig.SetOmitSessionToken(false);
            awsSigningConfig.SetShouldSignHeaderUserData(reinterpret_cast<void*>(const_cast<Aws::Set<Aws::String>*>(&m_unsignedHeaders)));
            awsSigningConfig.SetShouldSignHeaderCallback([](const Aws::Crt::ByteCursor *name, void *user_data) {
                Aws::Set<Aws::String>* unsignedHeaders = static_cast<Aws::Set<Aws::String>*>(user_data);
                Aws::String headerKey(reinterpret_cast<const char*>(name->ptr), name->len);
                return unsignedHeaders->find(Aws::Utils::StringUtils::ToLower(headerKey.c_str())) == unsignedHeaders->cend();
            });
            if (signatureType == Aws::Crt::Auth::SignatureType::HttpRequestViaHeaders)
            {
                Aws::String payloadHash(UNSIGNED_PAYLOAD);
                if(signBody || request.GetUri().GetScheme() != Aws::Http::Scheme::HTTPS)
                {
                    if (!request.GetContentBody())
                    {
                        AWS_LOGSTREAM_DEBUG(v4AsymmetricLogTag, "Using cached empty string sha256 " << EMPTY_STRING_SHA256 << " because payload is empty.");
                        payloadHash = EMPTY_STRING_SHA256;
                    }
                    else
                    {
                        // The hash will be calculated from the payload during signing.
                        payloadHash = {};
                    }
                }
                else
                {
                    AWS_LOGSTREAM_DEBUG(v4AsymmetricLogTag, "Note: Http payloads are not being signed. signPayloads=" << signBody
                            << " http scheme=" << Aws::Http::SchemeMapper::ToString(request.GetUri().GetScheme()));
                }
                awsSigningConfig.SetSignedBodyValue(payloadHash.c_str());
                awsSigningConfig.SetSignedBodyHeader(m_includeSha256HashHeader ? Aws::Crt::Auth::SignedBodyHeaderType::XAmzContentSha256 : Aws::Crt::Auth::SignedBodyHeaderType::None);
            }
            else if (signatureType == Aws::Crt::Auth::SignatureType::HttpRequestViaQueryParams)
            {
                if (ServiceRequireUnsignedPayload(serviceName))
                {
                    awsSigningConfig.SetSignedBodyValue(UNSIGNED_PAYLOAD);
                }
                else
                {
                    awsSigningConfig.SetSignedBodyValue(EMPTY_STRING_SHA256);
                }
            }
            else
            {
                AWS_LOGSTREAM_ERROR(v4AsymmetricLogTag, "The signature type should be either \"HttpRequestViaHeaders\" or \"HttpRequestViaQueryParams\"");
                return false;
            }
            awsSigningConfig.SetExpirationInSeconds(static_cast<uint64_t>(m_expirationTimeInSeconds));
            awsSigningConfig.SetCredentials(crtCredentials);
            return true;
        }


        SigningFutureOutcome sign(std::shared_ptr<HttpRequest> httpRequest, const AwsCredentialIdentityBase& identity, SigningProperties properties, const Aws::String& region, const Aws::String& svcName, long long expirationTimeInSeconds,
          Aws::Crt::Auth::SignatureType signatureType)
        {
            assert(httpRequest);
            assert(identity.expiration().has_value());

            const auto legacyCreds = [&identity]() -> Aws::Auth::AWSCredentials {
              if(identity.sessionToken().has_value() && identity.expiration().has_value())
              {
                return {identity.accessKeyId(), identity.secretAccessKey(), *identity.sessionToken(), *identity.expiration()};
              }
              if(identity.sessionToken().has_value())
              {
                return {identity.accessKeyId(), identity.secretAccessKey(), *identity.sessionToken()};
              }
              return {identity.accessKeyId(), identity.secretAccessKey()};
            }();

            auto signPayloadIt = properties.find("SignPayload");
            bool signPayload = signPayloadIt != properties.end() ? signPayloadIt->second.get<Aws::String>() == "true" : false;

            auto signerRegionOverrideIt = properties.find(smithy::SIGNER_REGION_PROPERTY);
            auto regionOverride = signerRegionOverrideIt != properties.end() ? signerRegionOverrideIt->second.get<Aws::String>().c_str() : region.c_str();

            auto signerServiceNameOverrideIt = properties.find(smithy::SIGNER_SERVICE_NAME);
            auto serviceName = signerServiceNameOverrideIt != properties.end() ? signerServiceNameOverrideIt->second.get<Aws::String>().c_str() : svcName.c_str();

            auto &request = *httpRequest;

            //don't sign anonymous requests
            if (legacyCreds.GetAWSAccessKeyId().empty() || legacyCreds.GetAWSSecretKey().empty())
            {
                return SigningFutureOutcome(std::move(httpRequest));
            }

            httpRequest->SetSigningAccessKey(legacyCreds.GetAWSAccessKeyId());
            httpRequest->SetSigningRegion(regionOverride);

            auto crtCredentials = Aws::MakeShared<Aws::Crt::Auth::Credentials>(v4AsymmetricLogTag,
                Aws::Crt::ByteCursorFromCString(identity.accessKeyId().c_str()),
                Aws::Crt::ByteCursorFromCString(identity.secretAccessKey().c_str()),
                Aws::Crt::ByteCursorFromCString((*identity.sessionToken()).c_str()),
                (*identity.expiration()).Seconds());

            Aws::Crt::Auth::AwsSigningConfig awsSigningConfig;

            bool success = createAwsSigningConfig(crtCredentials, request, serviceName, regionOverride, awsSigningConfig, signPayload, signatureType);

            if(!success)
            {
                AWS_LOGSTREAM_ERROR(v4AsymmetricLogTag, "Failed to get Auth configuration");

                return SigningError(Aws::Client::CoreErrors::MEMORY_ALLOCATION, "", "Failed to get Auth configuration", false);
            }

            awsSigningConfig.SetRegion(regionOverride);
            awsSigningConfig.SetService(serviceName);
            awsSigningConfig.SetExpirationInSeconds(expirationTimeInSeconds);

            std::shared_ptr<Aws::Crt::Http::HttpRequest> crtHttpRequest = request.ToCrtHttpRequest();

            auto sigv4HttpRequestSigner = Aws::MakeShared<Aws::Crt::Auth::Sigv4HttpRequestSigner>(v4AsymmetricLogTag);
            //This is an async call, so we need to wait till we have received an outcome
            Aws::String errorMessage;
            bool processed = false;
            //producer function
            sigv4HttpRequestSigner->SignRequest(crtHttpRequest, awsSigningConfig,
                [&request, &success, &errorMessage, &processed, this, signatureType](const std::shared_ptr<Aws::Crt::Http::HttpRequest>& signedCrtHttpRequest, int errorCode) {
                    std::unique_lock<std::mutex> lock(m_mutex);
                    m_cv.wait(lock, [&]{ return !processed; });
                    success = (errorCode == AWS_ERROR_SUCCESS);
                    if (success)
                    {
                        if (signatureType == Aws::Crt::Auth::SignatureType::HttpRequestViaHeaders)
                        {
                            for (size_t i = 0; i < signedCrtHttpRequest->GetHeaderCount(); i++)
                            {
                                Aws::Crt::Optional<Aws::Crt::Http::HttpHeader> httpHeader = signedCrtHttpRequest->GetHeader(i);
                                request.SetHeaderValue(Aws::String(reinterpret_cast<const char*>(httpHeader->name.ptr), httpHeader->name.len),
                                    Aws::String(reinterpret_cast<const char*>(httpHeader->value.ptr), httpHeader->value.len));
                            }
                        }
                        else if (signatureType == Aws::Crt::Auth::SignatureType::HttpRequestViaQueryParams)
                        {
                            Aws::Http::URI newPath(reinterpret_cast<const char*>(signedCrtHttpRequest->GetPath()->ptr));
                            request.GetUri().SetQueryString(newPath.GetQueryString());
                        }
                        else
                        {
                            errorMessage = "No action to take when signature type is neither \"HttpRequestViaHeaders\" nor \"HttpRequestViaQueryParams\"";
                            AWS_LOGSTREAM_ERROR(v4AsymmetricLogTag, errorMessage);
                            success = false;
                        }
                    }
                    else
                    {
                        Aws::OStringStream errStream;
                        errStream << "Encountered internal error during signing process with AWS signature version 4 (Asymmetric):" << aws_error_str(errorCode);
                        errorMessage = errStream.str();
                        AWS_LOGSTREAM_ERROR(v4AsymmetricLogTag, errorMessage);
                    }

                    processed = true;
                    m_cv.notify_all();
                }
            );

            //consumer
            {
                std::unique_lock<std::mutex> lock(m_mutex);
                m_cv.wait(lock, [&]{ return processed; });

            }

            return success? SigningFutureOutcome(std::move(httpRequest)) : SigningError(Aws::Client::CoreErrors::MEMORY_ALLOCATION, "", "Failed to sign the request with sigv4", false);

        }

        bool ServiceRequireUnsignedPayload(const Aws::String& serviceName) const
        {
            // S3 uses a magic string (instead of the empty string) for its body hash for presigned URLs as outlined here:
            // https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html
            // this is true for PUT, POST, GET, DELETE and HEAD operations.
            // However, other services (for example RDS) implement the specification as outlined here:
            // https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
            // which states that body-less requests should use the empty-string SHA256 hash.
            return "s3" == serviceName || "s3-object-lambda" == serviceName;
        }

        Aws::String m_serviceName;
        Aws::String m_region;
        std::shared_ptr<Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy> m_policy;
        //params that can be exposed later
        long long m_expirationTimeInSeconds{0};
        const bool m_includeSha256HashHeader{true};
        const bool m_urlEscape{true};
        const Aws::Set<Aws::String> m_unsignedHeaders{USER_AGENT,X_AMZN_TRACE_ID};
        const Aws::Crt::Auth::SignatureType m_signatureType{Aws::Crt::Auth::SignatureType::HttpRequestViaHeaders};
        std::condition_variable m_cv;
        std::mutex m_mutex;
    };
}